1. Field of the Invention
The present invention relates to a network interface apparatus for use in data communication over an IP (Internet Protocol) network and a method therefor. More particularly, the present invention is advantageously applicable to a gateway apparatus connected to a computer function for performing data communication such as a real-time G3 facsimile connected to the Internet for establishing smooth communication therebetween.
2. Description of the Background Art
Several related technologies, described below, have been proposed for data communication, communication control, and connection selection for use in systems with different transfer speeds or transmission rates.
First, in Japanese Patent Laid-Open Publication No. 96454/1992, there is disclosed a communication control system for adjusting transfer speeds for data communication between systems with different transfer speeds. This publication describes a system in which transfer speed conversion means is provided between two systems for controlling data transfer processing via control means. This system uses only one dual-port RAM, instead of a buffer memory such as a FIFO memory, to reduce the system cost.
Second, in Japanese Patent Laid-Open Publication No. 331164/1996, there is disclosed a communication control system for use in connecting to a plurality of types of LANs. This system has a buffer controller that sets up a buffer size at the start of data transfer processing. This buffer size defines the maximum data amount processible by one transmission/reception sequence according to the environment condition to increase data transfer efficiency.
Third, in Japanese Patent Laid-Open Publication No. 331348/1997, there is disclosed a network connection apparatus that selects destinations according to the protocol type. This apparatus has a pre-set table, via which a line best suited for the protocol of a received packet is selected for transmission, to increase user operability and reduce line costs.
In addition, in Japanese Patent Laid-Open Publication No. 178494/1998, there is disclosed a communication terminal, a communication system, and a communication control method. For example, when the continuous communication time is limited to a predetermined period of time as in the G3 protocol, the maximum data amount that can be sent is set by setting means based on the limitation time and the amount of transmission data. Control means of the system controls transmission based on this setting to send data smoothly.
Finally, in Japanese Patent Laid-Open Publication No. 334023/1998, there is disclosed electronic equipment that can be applied to network communication according to the TCP/IP (Transmission Control Protocol/Internet Protocol) protocol. When the equipment receives print output data from an upline network, it notifies a terminal or some terminals on a downline network, to which the equipment is connected, that the data has been received. And, upon receiving a data request from the terminal in response to this notification, the equipment sends the received data to the terminal. This method allows the user of a terminal on the downline network to recognize that the data has been received on the upline network and, between the real-time G3FAX and the IP network and terminates processing abnormally.